Native to tropical and subtropical Asia, basil is an annual herb so simple to grow that even first-time gardeners can plant it with confidence. It thrives in hot, humid weather and grows well throughout the South from spring until frost. Deer don't like it.
The normally 2-ft.-tall, bushy plant produces spikes of small white or pinkish flowers, but it's prized for its shiny green leavesoval, 12 in. long, with a clovelike fragrance and spicy-sweet flavor that make them indispensable in the kitchen. However, there are endless variations of the theme, including forms with purple or variegated foliage; dwarf globe or columnar habits; giant or tiny leaves; and white, pink, and purple flowers. Flavors cover a wide range, including anise, cinnamon, clove, coriander, lemon, and lime.
Fresh basil leaves are a must for summer salads, especially with tomatoes. In fact, it is critical for pesto, Italian, Indian, and Southwestern cuisine. Used fresh or dried, its leaves lend a pleasant, mildly sweet flavor to sauces and cooked dishes of all sorts. The most flavorful leaves are from younger stems that have not yet borne flowers. And don't overlook basil as a cut flower. Both green- and purple-leaved stems give a bouquet of zinnias the scent of summer.
There are too many selections to list them all here, but the following is a sampling of what's available.
Big leaves. 'Italian Large Leaf', 'Large Green', 'Mammoth Sweet', 'Napoletano', and 'Rapper' have especially big leaves; use them as wraps for appetizers or in place of lettuce on a sandwich.
Compact plants. Try 'Aristotle', 'Boxwood', 'Finissimo Verde a Palla', 'Genovese Compact', 'Greek' ('Spicy Globe'), 'Green Ball' (no blooms), 'Magical Michael', 'Marseillais Dwarf', 'Pluto', and 'Red Ball' (purple with green edges), any of which make small-leafed globes of basil flavor. 'Genovese Compact' has full-size leaves and remains 1618 in. tall.
Columnar plants. Try 'Greek Columnar' (2436 in. tall, 9 in. wide) and 'Pesto Perpetuo' (up to 48 in., does not flower).
Flavored leaves. Because basil comes in so many flavors, taste a leaf, if possible, before you buy. Most of the selections describe their flavors: 'Cinnamon', 'Clove', 'Cuban' (spicy), 'Holy' (Thai cuisine), 'Lemon', 'Licorice, 'Lime', 'Mrs. Burns' Lemon', 'Sweet Dani' (intense lemon, larger leaves), or 'Sweet Thai Basil' (flavor of anise and cloves).
Perennial types. Grow these outdoors in virtually frost-free climates or indoors: 'Magic Mountain' (3 ft.) or 'Pesto Perpetua' (to 4 ft., with light green leaves that have creamy variegation). 'African Blue' (to 5 ft. tall) has showy blooms almost like purple salvia, and the bloom spikes do not seem to compromise the growth of the plant.
Best for pesto. Start with a Genovese type such as 'Aroma 1' or 'Aroma 2', 'Emily' (compact form), 'Genovese', 'Nufar', 'Profumo', or 'Superbo'; or use a standard selection such as 'Sweet Basil'.
Purple foliage. These O. b. purpurascens selections can be touchy to grow, but they are beautiful and much used in Asian cooking: 'Amethyst' (Genovese type), 'Purple Ruffles', 'Red Lettuce Leaved', 'Red Osmin' (an improved 'Dark Opal'), and 'Red Rubin'.
Disease tolerant. Look for 'Aroma 1', 'Aroma 2', 'Habana', 'Harlekin' (green and purple), 'Nufar', and 'Red Ball' (purple with green edges).
Ornamental. 'Chistmas' has glossy, medium leaves, purple flowers, and fruity taste. 'Siam Queen', to 2 ft. tall, is a licorice-flavored basil that's good for Thai and Vietnamese dishes; produces showy purple flowers. 'Magical Michael' forms a neat mound to 112 ft. tall and wide and has both culinary and ornamental value. Dwarf sweet basils form dense, compact plants under 1 ft. tall; they're good for edging and also do well in containers. Recommended selections include 'Finissimo Verde a Palla', 'Minette', 'Pluto', and 'Spicy Globe'.
Sow seeds of any basil in early spring indoors, or sow seeds or set out nursery plants after all danger of frost has passed and the soil has warmed, about the time you plant tomatoes. Choose a spot with well-drained soil, 6-8 hours of sunlight per day. Plant seeds 14 in. deep. When seedlings are 23 in. tall, thin them to 1122 ft. apart. Alternatively, space transplants about 1012 in. apart. Use a generous amount of compost in the soil at planting time, and, if needed, use a timed-release fertilizer as directed on the label.
Where the growing season is long, these annual plants complete their lifecycles by flowering and setting seeds. This also means that plants stop growing flavorful leaves. Postpone the inevitable by pinching out bloom spikes when they form. You can also cut plants back by a third, even if you don't have time to make pesto. Pruning more severely cuts into older stems that will not sprout as readily. Feed plants lightly with compost tea or a similar liquid product to spur new leafy growth. Two branches will grow wherever a single branch is cut. Plants will produce new leaves until it begins to bloom again.
Because flowering is associated with high temperatures, Southern gardeners should mulch plants to help keep the soil cool. Gardeners in the warmest areas of the South may find that basil will actually grow better with a little afternoon shade. If your season is long, replant in late summer for a second crop. Growth will continue until temperatures drop below 50F. Basil will be blackened by the slightest frost, so when the first freeze is forecast, it is time to process your basil, whether you make pesto for the freezer or dry it for winter use.
Basil is susceptible to fusarium wilt, which causes plants to collapse in a day. Defeat it by growing tolerant selections and never plant basil in the same bed more than once every 4 years. Alternatively, plant in containers.